Here are cheats for Guitar Hero II. Check em out… Cheater!

Enter The Following Cheats in the main menu of the game.

Unlock All:
blue, yellow, orange, red, orange, yellow, red, yellow, red, yellow, red, yellow, red, yellow, red, yellow

Air guitar mode:
Yellow, Yellow, Blue, Orange, Yellow, Blue.

Performance mode:
Yellow, Yellow, Blue, Yellow, Yellow, Orange, Yellow, Yellow.

Hyper speed mode:
Orange, Blue, Orange, Yellow, Orange, Blue, Orange, Yellow. Repeat the code to disable.

Master hyper speed :
Orange, blue, blue, yellow, red, blue, yellow.

Eyeball head crowd:
Blue, Orange, Yellow, Orange, Yellow, Orange, Blue.

Monkey head crowd:
Orange, Blue, Yellow, Yellow, Orange, Blue, Yellow

Flaming head:
Orange, Yellow, Orange, Yellow, Orange, Yellow.

Horse head:
Blue, Orange, Orange, Blue, Orange, Orange, Blue, Orange, Orange, Blue.

Pro-Face Off mode:
Beat the whole game in Medium. Lets players face off while playing the same notes.

Unlockable guitars:

Unlockable basses:

Grim Ripper plays Les Paul:
This cheats works with Career mode. If you don’t have the Grim Ripper, go buy him from the store. Choose the Grim Ripper as your character, go all the way back to the main menu, then re-enter your career. The Grim Ripper should now be playing a Les Paul.

Anyone plays the Scythe:
This also happens in Career mode. If you don’t have the Grim Ripper, get him from the shop. Go to any difficulty setting and choose anyone who’s not the Grim Ripper. Then, go to another difficulty level and choose the Grim Ripper. Finally, go back to your original difficulty setting, and whatever character you picked should be playing the Scythe.